Such a coupling assembly is, e.g., known from DE 37 10 772 A1. This coupling assembly serves for coupling a trailer coupling part on the tractor vehicle side to a support plate mounted on the tractor vehicle. Using the known coupling assembly one and the same tractor vehicle may be equipped with different trailer coupling parts on the tractor vehicle side at different points of time, i.e. for example a jaw coupling and a ball end coupling may be exchanged. The known coupling assembly is constructed in the manner of a bayonet lock, i.e. in order to bring about coupling a trunion provided with arresting projections, which trunion is positioned on the trailer coupling part on the tractor vehicle side, is introduced into a recess in the support plate, the recess having undercuts, until the trailer coupling part and the support plate are in mutual abutment with respective contact faces, and subsequently, by rotating the trailer coupling part in a substantially orthogonal direction to the contact faces, the arresting projections are caused to positively engage with the wall sections of the support plate which confine the undercuts towards the contact face.
In order to be able to avoid self-actuated uncoupling of the two coupling elements, support plate and trailer coupling part on the tractor vehicle side the known coupling assembly is provided with a securing element in the form of a cap which may be folded over the two coupling elements manually after coupling. It is also possible not to fold this securing cap over the support plate and the trailer coupling part so that coupling can automatically be released when there is sufficiently high torque acting around a direction substantially orthogonal to the contact face.